|
Signal Frequency and
Channel Information
As I have stated on my galaxy
mod page, you should know about the wavelength when doing a
mod on a galaxy dish.
My galaxy mod is out by a few mill but doesn't make a bit
difference. May only have a loss of 1-2dB because the
wavelength will be out a little.
The dipole of the ex-galaxy
dish is 1/2 wavelength (64mm), and 1/4 wavelength (32mm).
Important dimensions you need
are:
- Length of the dipole is
1/2 wavelength
- Length of the balun is 1/4
wavelength
- Ratio of inner diameter of
copper tube to outer diameter of brass rod
The 802.11b standard uses
2.412GHz to 2.484GHz frequency range.
The centre of that frequency range makes the 1/2 wavelength
61mm, and 1/4 wavelength is 30.5mm.
To work out the wavelength of
a frequency. Here is the formula:
|
Y = V / F |
|
F = Frequency |
|
V = Speed of light ( 3 x 10^8
m/s) |
|
Y = Wavelength in metres |
Here is how its worked out:
|
Y = V / F |
|
Y = 3 X 10^8
/ 2.447 X 10^9 |
|
Y = 0.1225991 m |
|
Y = 122.5
x 10^-3 m (122.5mm
- full wavelength) |
| Which makes the 1/2
wavelength 61mm, and 1/4 wavelength 30.5mm |
List
of Channels, Frequencies and Wavelengths
|
Channel
Number |
Frequency |
Full
Wavelength |
| Channel
1 |
2412Mhz |
124.3mm |
| Channel
2 |
2417Mhz |
124.1mm |
| Channel
3 |
2422Mhz |
123.8mm |
| Channel
4 |
2427Mhz |
123.6mm |
| Channel
5 |
2432Mhz |
123.3mm |
|
Channel
6 |
2437Mhz |
123.1mm |
| Channel
7 |
2442Mhz |
122.8mm |
| Channel
8 |
2447Mhz |
122.5mm |
| Channel
9 |
2452Mhz |
122.3mm |
| Channel
10 |
2457Mhz |
122.1mm |
| Channel
11 |
2462Mhz |
121.8mm |
| Channel
12 |
2467Mhz |
121.6mm |
| Channel
13 |
2472Mhz |
121.3mm |
| Channel
14 |
2484Mhz |
120.7mm |
Frequency
bands and EIRP Limits
|
Frequency
Band (MHz) |
Maximum
Equivalent Isotropically Radiated Power (EIRP)
|
| 915 to 928 |
1 watt |
|
2400 to
2483.5 |
4 watts
(devices other than
frequency hopping devices with a bandwidth greater than
1 MHz) |
|
2400 to
2483.5 |
500
milliwatts
(frequency hopping devices with a bandwidth greater than
1 MHz) |
| 5725 to 5875 |
1 watt |
Reference:
http://www.aca.gov.au/aca_home/publications/reports/info/spreadsp.htm
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